---
title: associatedIndex
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsorderedcollectionchange/associatedindex
---

# associatedIndex

When this property is set to a value other than NSNotFound, the receiver is one half of a move, and this value is the index of the change’s counterpart of the opposite type in the diff.

## Declaration

```swift
var associatedIndex: Int { get }
```

## Discussion

Discussion Pairs of changes with opposite types that refer to each other represent the index location of their counterpart with the associatedIndex property. The following example creates a diff where the object @”Red” moves from index 8 to index 3: NSOrderedCollectionDifference *diff = [[NSOrderedCollectionDifference alloc] initWithChanges:@[     [NSOrderedCollectionChange changeWithObject:@"Red" type:NSCollectionChangeRemove index:8 associatedIndex:3],     [NSOrderedCollectionChange changeWithObject:@"Red" type:NSCollectionChangeInsert index:3 associatedIndex:8] ]]; A move pair can have a different object in its removal and insertion changes, which can imply that the change represents moving and changing or replacing an element. Diffs that controller(_:didChangeContentWith:) passes to delegates of NSFetchedResultsController communicate that an object changed even when its position in the results is unaffected. note: Don’t ignore a move when the indexes of its changes are the same. The calculated difference from @[@”A”, @”B”, @”C”] to @[@”C”, @”B”] may legitimately produce a diff where the change removes the object at index 0 and the object at index 1 moves to index 1. Ignoring the move produces the incorrect result @[@”B”, @”C”].

## See Also

### Accessing the Change

- [changeType](foundation/nsorderedcollectionchange/changetype.md)
- [index](foundation/nsorderedcollectionchange/index.md)
- [object](foundation/nsorderedcollectionchange/object.md)